Yes, the gastrointestinal tract is a very prominent part in fact.
Yes
Yes, eating boogers does help the immune system. The immune system (the stomach) will take in the booger, and pass it down to your "Junk" Section.
If bacteria get into the stomach of a human the first line of defense of the immune system that will potentially stop the bacteria is the gastric juice in the stomach.
Your immune system fights off disease carrying cells.
In the Stomach, or Intestines (Look a little deeper), there is some bacteria that helps with digestion, because they speed up the process. The Immune System recognizes this, and basically leaves them to do their job.
your immune system and your White blood cells produce antibodies
skin, stomach acid, mucous membranes and endothelial tissues then Innate immune system which is cascade of reactions of some 25 proteins produced in the spleen and liver marking them to be eaten by immune cells called phagocytes (monocytes, neutrophils and macrophages)
Yes. The reduced absorption of vitamins and minerals waekens the immune system. Thiws allows a fungus to take hold. This can lead to stomach cancer.
Acquired Immune System or Adaptive immune System
The Immune System
It would be their immune system.
The adaptive immune system is activated if the innate immune system is unable to control the infection.